Conventional fracture closure models typically assume homogeneous formation. This assumption renders complex fracture closure pressure analysis during shut-in insufficient at present. In this paper, we use a cohesive zone method (CZM)-based finite element model to obtain the fracture closure pressure and minimum horizontal principal stress of the major fracture and the branch fracture based on pressure fall-off analysis. Key factors including leak-off rate, injection time, and stress anisotropy are discussed in detail. A quantitative relationship between fracture closure pressure and these factors is plotted to reduce or eliminate the errors caused by conventional fracture injection diagnostic models. The results show that leak-off rate, injection time, and stress anisotropy have a significant effect on the fracture closure process. Fracture closure in naturally fractured formations is a slow process, and the early closure pressure represents the closure of the branch fracture, which is much higher than the minimum horizontal stress. This investigation provides new insight into how to estimate the in-situ stress in naturally fractured reservoirs.

常规裂缝闭合模型通常假设均质地层。这一假设导致目前关井期间复杂的裂缝闭合压力分析不足。在本文中，我们使用基于粘性区法（CZM）的有限元模型，基于压力衰减分析获得主裂缝和分支裂缝的裂缝闭合压力和最小水平主应力。详细讨论了泄漏率、注入时间和应力各向异性等关键因素。绘制裂缝闭合压力与这些因素之间的定量关系，以减少或消除由常规裂缝注入诊断模型引起的误差。结果表明，漏失率、注入时间和应力各向异性对裂缝闭合过程有显着影响。天然裂缝地层裂缝闭合是一个缓慢的过程，早期闭合压力代表分支裂缝的闭合，远高于最小水平应力。这项调查为如何估计天然裂缝储层的地应力提供了新的见解。